Help for SRCHEDGE

PURPOSE:
	To find the angle in degrees of the transition edge of an input image.  
	The transition edge is the line at which a vast difference in DN
	values is found.

EXECUTION:
        
	srchedge inp=in.img out=out.img angle=angle [optional-parameters]


METHOD:

        INPUT IMAGE:

        Only black and white halfword VICAR images are valid.	The input
	image has only dark and light DN values with one side of the image
	dark and the other light.  A distinctive straight line created by
	the transition edge from dark to light or light to dark separates
	the two values.


        ddddddddddddddddddddddddll
        dddddddddddddddddddddlllll
        ddddddddddddddddddllllllll
        dddddddddddddddlllllllllll
        ddddddddddddllllllllllllll      d=dark DN value
        ddddddddllllllllllllllllll
        ddddllllllllllllllllllllll      l=light DN value
        dlllllllllllllllllllllllll
        lllllllllllllllllllllllll|
        llllllllllllllllllllllllll
        llllllllllllllllllllllllll
        llllllllllllllllllllllllll


        PROCESSING:

        Srchedge does the following:

                1) Finds the transition edge where the dark DN value
                   and the light DN value come together.
                2) Creates an output image file that is the same as the
		   input file except the transition edge is marked with DN
		   values of 20,000.
                3) Does a least squares fit on the points making up the
	           transition edge.
                4) Gets the angle of the line created by the least squares
		   fit and returns it in parameter angle.

	The angle is measured as follows:

		1) Preliminary angle A is obtained such that -90.0< A <=90.0
		2) Then there are 6 cases:
			A. Dark side on left  and A>0   =>  angle = 360.0 - A
			B. Dark side on right and A>0   =>  angle = 180.0 - A
			C. Dark side on left  and A<0   =>  angle = 180.0 - A
			D. Dark side on right and A<0   =>  angle = -A
			E. Horizontal w/ dark on top    =>  angle = 180.0
			F. Horizontal w/ dark on bottom =>  angle = 0.0

	Note:  A local variable of type real for parameter angle must be
	       declared by the user.

HISTORY:
Oct 24, 1997	RRD	Improved help section.  Fixed bug on Solaris by
			changing variable cut from unsigned int to int.
			Commented out line in fitpts that calculates sigma
			because it generates DOMAIN error. 
Jul 22, 1997	RRD	Ported to UNIX.
Mar 28, 1996  Y Kwon	Wrote original version.

COGNIZANT PROGRAMMER:  Young Kwon